a) Field of the Invention
This invention relates to a hydraulic coupling for use with a vehicle drivetrain within a housing containing hydraulic fluid to rotatively couple a pair of rotary members about a rotational axis; for example, a speed sensitive limited slip differential.
b) Background of Related Art
Many types of hydraulic devices have utilized internal gear sets, which are often called gerotors or rotors. Such devices can be used as pumps where shaft work is converted to hydraulic work and as motors where hydraulic work is converted to shaft work. In an internal gear pump or motor, an inner gear having outwardly directed teeth cooperates with an external gear having inwardly directed teeth so that fluid chambers therebetween increase and decrease in volume as the inner and outer gears rotate in a housing. By connecting the inlet and outlet of the device to the proper location along the sides of the gear set, the variable displacement chambers receive and discharge hydraulic fluid so that the device can function as a pump or motor. A shaft or other mechanical device can be connected to either the inner or outer gear depending upon the type of device.
Many of the internal gear pumps and motors of the prior art utilize a housing having a fixed inlet and outlet valve port. In other gerotor pumps and motors, a rotary valve plate or disc is used.
The gerotor pump has previously been utilized to couple rotary members of a vehicle drivetrain, particularly a limited slip differential mechanism. However, prior art gerotor pump devices suffer from inadequate or inefficient control of the torque curve and torque transfer characteristic of the pump device. Conventional check valves and other control valve systems suffer from excessive variability in torque distribution, they are difficult to handle and assemble and they require expensive machining in the differential case. Additionally, the conventional valve systems do not adequately control the torque transmission characteristics for the pump.
The need therefore exists for an improved and efficient control valve system that provides an effective hydraulic flow path.